The autograft bones (autogenous chips) harvested from the bones of the same person during the same operating procedures or allograft (living tissue transferred between two genetically different individuals of the same species), cut into smaller pieces, may create morselized bone. Morselized bone, dry or mixed with selected fluids, used as bone grafts in surgical procedures to repair or augment skeletons.
The available bone mills generally suffer from inability to produce, consistently and repeatedly, morselized bone with needed particle-size distribution profile to produce needed dense bone graft with desired biomechanics properties, within the time constrain of surgical procedures.
The available manually operated bone mills suffer from inability to produce adequate amount of morselized bone within the time constraint during the surgical procedures. Considering the cost per minute associating with the surgical hospital room and facilities, and the supporting staff, the low cost manually operated bone mills may lose their price advantage; and, indeed, may effectively be significantly expensive, instead. The manually operated bone mills may be suitable for surgical procedures requiring small amount of morselized bone.
Furthermore, the available powered bone mill apparatuses suffer from either transferring heat to the milled bone particles during the milling process that may damage the particles, or requiring an operator to attend the mill skillfully pushing the hard bone material against a rasp for producing bone particles, which may incur additional personnel costs.
For example, in the case of bone mill functioning similar to a coffee grinder, the milled particles and the material remains in the same milling chamber until the end of the milling procedure; and during the milling time, milled particles unnecessarily undergo impacts with each other and with the dull blade, generating heat energy that may damage the milled particles. Further, bone mill of coffee grinder design often fail to complete the needed milling; it creates fine, dust-like, milled bone particles with not-milled marble-like bone pieces that are beyond the mill's ability to mill. Therefore, these types of powered bone mills suffer from inability to provide morselized bone with the desired particle-size distribution profile, and having inherent problems with heating and damaging milled particles.
For another example, the powered bone mill functioning as a crusher often produces large bone slivers that may not be suitable for utilization in bone graft; under the constrained surgical time, the trained operator may have to recycle the first time-milled particles through the mill until achieving the desired finer bone particle-size distribution profile. These types of bone mills may suffer from inability to provide morselized bone with a predetermined particle-size distribution.
In some other cases, such as when the bone mill function as a powered cheese grater, a trained operator must push the bone against a rotating rasp hoping that the rasp would not clog and the operator may not face unclogging problem under time constrain during a surgical procedure. These types of bone mills often suffer from inability to provide morselized bone with the desired broad particle size distribution and requiring additional costly trained operator.
In all cases, none of the bone mills in current use may produce morselized bone with the needed particle-size distribution profile as N. T. Brewster, et al, discovered through their research (Mechanical consideration in impaction bone grafting, THE JOURNAL OF BONE AND JOINT SURGERY, Vol. 81-B, No. 1, January 1999).
Accordingly, a need may exist for an improved self-clearing rasp system capable of self-generating forces for pushing material against the rasp surface for providing an automatic milling apparatus capable of consistently providing superior morselized bone with similar particle-size distribution profile as planned.
Therefore, the main object of the present invention is to provide a self-clearing rasp system with self-generating forces for pushing the material against the rasp that may eliminate the need for skilled operator involvement.
It is another object of this invention to provide a self-clearing rasp system capable of consistently and repeatedly producing morselized bone with similar particle-size distribution profile within the constrained time limitation during a surgical procedure, regardless of the hardness and density of the bone material.
Moreover, it is another object of this invention to provide a self-clearing rasp system providing capabilities for predictably shifting the mean and broadening the standard deviation of the milled particle-size distribution profile during a given surgical procedure with the same rasp system.
Further, another object of this invention is to provide examples of automatic milling apparatuses utilizing said self-clearing rasp systems for automatic milling bone material at low temperature, repeatedly and efficiently producing bone particles with similar particle-size distribution profile as planned.